Lock tokio::sync::Mutexfrom synchronous code

[dpc]

Is your feature request related to a problem? Please describe.
I need to use async Mutex (because I need to lock between async yield points), but at the same time I need to share (and lock) it from some synchronous code.

Describe the solution you'd like
lock_blocking method on Mutex (and corresponding on RwLock) that allow locking the mutex from synchronous code.

Describe alternatives you've considered
Maybe there's a library that can do it already? I'm having trouble finding it though.

[Darksonn]

You can do this by calling futures::executor::block_on(mutex.lock()), though it could still make sense to add this. We have something similar for the mpsc channel.

[hi-rustin]

I am working on this.

[hi-rustin]

@dpc Can we close this issue now?

[Darksonn]

Oh, I didn't notice that the PR didn't include a keyword to auto-close it.

[LeonarddeR]

Note that in the initial comment of this issue, equivalent synchronous methods were requested for RwLock. This wasn't covered by #4130 but #4425